This invention relates to pipeline inspection apparatus and in particular concerns an apparatus for the manipulation of a camera or other examination device along a lateral pipeline.
Specifically, the apparatus is suitable for manipulating a camera to enable it to be inserted into and projected along a lateral pipeline which meets a main pipeline at an angle. A lateral pipeline may be provided, for example, to provide connection between a domestic dwelling and a main sewer or a main gas line. Frequently, there is a need for inspection of the lateral pipeline in order to ascertain its need of repair, or for the purpose of detecting a leak.
There are known TV inspection apparatus which can be inserted in and moved along main pipelines and passageways which are located underground, a TV camera sending back signals to a remotely located monitor, for example, in an inspection truck located at ground level. Wood U.S. Pat. No. 4,677,472 of June 30, 1987, entitled "Apparatus For Inspecting the Interior of a Pipeline", discloses apparatus for enabling the inspection of lateral pipelines or passageways, and in particular for permitting such inspection to be accomplished from the main pipeline. This is important because inserting the inspection camera from the consumer end of the lateral pipeline, i.e., from a domestic dwelling, is in the majority of cases unacceptable to the occupier of the dwelling. That patent discloses a driven pulley-like arrangement for engaging and driving the cable to which the TV camera is connected, thereby pushing the TV camera into and along the lateral pipeline.
It has been found that the apparatus of the aforesaid patent, while effective, is not sufficiently reliable, particularly with regard to the accuracy with which the TV camera is oriented relative to the lateral pipeline and the positiveness of the projection of the TV camera into and along that lateral pipeline. Because lateral pipelines may extend from the main pipeline at varying angles, without accurate initial alignment of the camera the camera will either not enter the lateral pipeline or will enter it in a manner causing it to impact against the wall of that lateral pipeline rather than being pushed through the pipeline opening. In addition, since pipelines often contain impediments to the passage of a camera therethrough, such as accumulations of debris, it may be necessary to exert strong force on the camera to push it through or past such obstructions, and the pulley drive on the camera cable in the apparatus of the aforesaid patent would sometimes slip when there was resistance to the movement of the camera along the lateral line.